Apparatus for recovering gasoline from natural gas



J. B. GARNENv AND s. c. PRESTON. APPARATUS FOR RECOVERING GASOLINEFROM NATURAL GAS.

APPLICATION FILED` Nov. 21.V `|'9 19.

Patented Nov. 28, 1922.

2 SHEETS-SHEET l- INVENTORS 2 SHEETS-SHEET 2.

Patented Nov. 28, 1922.

I. B. GARNER ANDS. C. PRESTON..

APPARATUS IOR REcovERING GAsouNE FRoM NATURAL GAS.

APPLICATION FILED NOI/.21. I9I9.

Patented Nov. 2S, 1922.

STIES 'earner eerie;

JAMES GARNER AND SYLVESTER C. PRESTON, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS, BY MESNE ASSIGNMENTS, TO HOPE CONSTRUCTION AND REFINING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWARE.

APPARATUS FOR RECOVERINGV GASOLINE FROM NATURAL GAS. Y

Application led November 21, 1919. Serial No. 339,555.

To all whom it Amay concern.'

Be it known that We, JAMES B. GARNER and 'SYLvEs'rnn C. PRESTON, residing at Pittsburgh, in the county of .Allegheny and State of Pennsylvania, both citizens of the llnited States, have invented or discovered certain new and useful Improvements in Apparatus for Recovering Gasoline from Nat'- ural (las, of which improvements the following is a specification.

In United States Letters Patent No. 989,927, granted to G. M. Saybolt, there is disclosed apparatus for obtaining naphtha or gasoline from combustible gas of natural origin and underground source, that is to say from natural gas. The apparatus, briefly characterized, consists of means for bringing the natural gas vWhen under pressure into absorption contact with a gasoline-absorbing menstruum, for the purpose of separating from the gas such of its components as|are normally liquid at atmospheric temperature and pressure,'and in means for subsequently separating from the inenstruum the gasoline so absorbed.

The objectof our present invention is to improve the apparatus-there disclosed and characterized generally as above.y The improved processwhich is accomplished in the operation of the apparatus here described, is described and claimed in a colpending. application, iled June 2', 1919, Serial No.y 301,165.

In the practice of our present invention means are provided by which natural gas is passed successively through two bodies of gasoline-absorbing menstruum, preferably a lioluid-petroleumV hydrocarbon of specific gravity rangin from about 28 to 55 Baume atl gahrenheit, these two bodies of menstruum being circulated and controlled in such manner that largelyv increased percentages of the' gasolinecontent of the natural gas are economically recov-- ered.

The first body of menstruum through which the gas passes is, by the means presently to be described, so circulated that,

preferably in minutely subdivided state, sub-` stantially the same bodies of menstruum contact again and again v with the advancing stream of gas. By thus increasing the number of contacts (and preferably increasing also the areas of contact) which the menstruum.makes with the gas, We have found that, due to absorption of gasoline from the gas, the Baume gravity of the menstruum may be raised (that is to'say, the specic' efo struum through which the gas passes be circulated and controlled in the manner presently to be explained. Among the important advantages of thusbuilding up the Baume gravity of the menstruuin, these incidental ones may be noted: First, much smaller quantities of menstruum are needed for absorbing, carrying and giving up in the still a unit volume ogasoline; and, second, when the menstruum is lused in closed cycle, as is the usual practice, the necessarycooling facilities for cooling the menstruum after it leaves the still are of much smaller extent.y 'We have found that by improving absorption conditions the menstruum as it absorbs gasoline may be caused to pass through relatively Wide ranges of Baume gravity, and accordingly largely increased percentages of the gasoline content of a stream of natural gas may be absorbed. In practice We have found that thus gasoline may be absorbed to a degree nearly approaching the theoretically maximum limit. That theoretical limit is the point Where the partial pressure oflthe gasoline vapor remaining in the gas is equal to the vapor tension of the gasoline in the menstruum. As a specific example, we have found that, conditioned upon proper control of the second body of menstruum al- Iready 'alluded to and described hereinafter the gasoline may be so completely absorbe from the gas that there Will remain in the gasl only about lifteen gallons of gasoline of menstruum.

per million cubic feet of gas (the gas being measured at a pressure of'eight ouncesabove atmospheric and at a temperature of 60 E),

whereas in 'the process heretofore usually practiced there still remains in the gas after absorption has been completed, from fifty to ninety gallons of gasoline per million cubic feet of gas, under the same conditions of pressure and temperature.

Still further we have found that, by repeatedly bringing substantially the same bodies of inenstruunr (we refer to the first bodyof menstruum) into absorption contact with the stream of gas, the lighter combustible constituents of the gas which, on the initial contact, and before the specific grav 4ity of the menstruum has been substantially passes, and to which allusion has more than once been made already, is so controlled, and the contact which the gas makes with it so controlled, that the decrease of specific gravity, that is to say, the rise in the Baume scale, will. be but small, as compared with that which is brought about in the first body `Preferably the specific gravity otE thissecond body of menstruum is not allowed to decrease more than would be indicated by a rise of 1C- n.inthe Baume scale. We have found that the beneficial results described above, arising from the improved absorption conditions in the meeting of the streamlof gas with the first body of menstruum, will be realized only by controlling conditions of absorption in the second body of menstruum to the end just indi cated.

The areas of "Contact between the advancing stream of gas and the first body of menstruum may be increased in any` suitable manner z-by means of' spray nozzles for example, or by the use of a coke tower as it is called, that is to say, a-chamber filled with inert broken material, often lumps of coke, through which the gas ascends While the menstruurn percolates downward. The second body of menstruum is preferably main-- tained in the formof a pool through which the gas bubbles. Such a pool will remove from the gas particles of menstruum carried on in the stream from the first absorber.

manici It is not necessary, however, that the second body of menstruum be maintained as a pool, and in the sequel it will appear that the secf ond absorber may., for example, be of the coke-tower type.

In the accompanying drawings, the ap paratus of our present invention is diagramn matically illustrated. Figure 1 shows a complete lay-out of an operative plant; and Figures 2 and 3 show absorption units such as may be substitutedlfor the units of the form specifically shown in Figure 1.

Referring first to Figure 1, the course of the natural gasfrom a suitable source of suppl and under any desirable pressure is as fo lows: lt comes through a pipe 1 and enters the absorber 2. From absorber 2 it may advance in either of two courses: it mav flow through a pipe 6 to absorber 9, which is the second absorber, or it may, passing from' absorber 2, flow through pipe connection 11 into the coke tower 12, and from the coke tower 12 pass through the pipe 11i to the second absorber 9. Valves 415, 16 and 17 are provided, so placed, as will be understood on inspecting the drawings, that the stream` of gas may flow in either one of the two courses indicated, as may be desired. The absorber 2 is, as shown, preferably a horizontally' disposed cylindrical chamber in which, as will presently be explained, the circulation of absorbent menstruum is arrested, and in' which there is a minute mingling of gas with menstruum or, stated in other words, where the areas of contact between gas and menstruum are greatly extended.' This is accomplished by spraying the menstruum through the advanclng stream or' gas and, as will be observed, there are in this chamber 2, three sets of spray nozzles for eli'ecting this end, 3, l and 5. The second absorber 9, though as has already been said it need not be, may conveniently-besuch as shown-in Figure 1. This second absorberl), as here shown, consists also of a horizontally disposed cylindrical chamber in which, as will presently more fully appear, the circulating stream of menstruum is arrested in, its flow; and in which it is maintained in a pool; and through which pool the advancing gas is caused to bubble by flowing out through a perforate header 7. lt passes out from this absorber by being collected again in another perforate header 8, from which it ad-y vances into the pipe line 10, and through the pipe 10 to the point of consumption.

The coke tower 12 alluded to needs no elaborate description, in view of what has already been said. lt is a tower preferably of cylindrical shape and vertically disposed, filled through the greater part of broken inert material 13. such as stone or coke. The gas is admitted in the lower portion of this tower, and passes upward through the body of broken inert material, while menstruum introduced -in the upper part of the tower, descending, percolates through this Asl has already been intimated, the mens struum in the second absorber and the I nen struum in the first absorber are preferably parts of, one continuous stream of menstruuml flowing in closed circuit, and the line of fiow is counter-current to the stream of gas. This preferable arrangement is shown in Figure 1 ofthe drawings, and the line vof circulation of the menstruum will now be followed. Beginning at the pump 18,y the menstruum driven by that pump flows through pipe -19 into the absorber 9, where retardation afforded by theenlarged chamber with its contracted exit effects retardation ofthe stream and formation of the pool of ymenstruum already alluded to. From the absorber 9 the menstruum is caused to advance through a pipe 21, preferably by means of a second pump 20, and

' through a continuation 22 of the circulation pipe, into one or another oftwo lines of flow: either directly through header 25, to' which several spray nozzles 3 are attached, into absorber 2, or through a pipe 26 into the top of the coke tower 12, and out again from the coke tower 12, -through pipe 28, into the 'pipe 22 leading to header 25. A proper setting of valves 51,- 52, and 53 will determine |whether or not the menstruum flowing from the second absorber into the first absorber travels through the coke tower. A pump 27 may be employed in connection Wlth the coke-tower, to pump the menstruum as it passes from the coke tower on into the line which leads to header 25. The construction of the coke tower has been sufficiently indicated, unless it be thatv it remains `-to say that the menstruum introduced near the top of the tower is preferably sprayed upon the column of broken material which fills the tower. And this is indicated inthe drawing.

From the absorber 2 the menstruum laden with the absorbed gasoline passes into a sump 29 and from sump 29, through a pipe 31 which is controlled by a stop cock 41, into a vent tank 42, where such normally gaseous components of the burden incidentally absorbed by the menstruum are, at atmospheric pressure, allowed to escape.

From the yent 42 the gasoline-laden menburden which the menstruum has carried struum passes from'the still through pipe 47. 'It enters first the heat exchanger 44, passes thence through the pipe 48 to the cooler 49, and from the cooler flows through pipe 50 to the pump 18, where the circuit described is now completed.

It will of course be understood, and th matter is made plain in the Saybolt specilication referred to, that the still, t-he heat exchanger, and the cooler are introduced in` an exemplary 'way merely, as preferred apparatus b which a gas-carrying menstruum is re ieved of its burden, but other appliances might be employed and other principles of separation be resorted to than the heat exchanger and the still. As we have just said, the illustration in this respect is exemplary and no more.

Coming back now to the absorbers 9 and 2, it remains to explain how that condition is brought about which,n the foregoing part of the specification, has already been alluded to: a condition, namely, of relatively great absorption in the first absorber 2 and relatively small absorption in the second absorber 9, with a correspondingly large drop in specific gravity as the menstruum passes through absorber 2, and only a' small drop in specific gravity as it passes through absorber 9. This is brought about of course by affording in absorber 2 relatively more favorable conditions of absorption than in absorber 9, and these relatively better' conditions of absorption in absorber 2 may consist of either one or both of two absorbing factors: area of contact and time of contact. There is a pipe connection 33 from sump 29 to headers 36' and 37 which, like header 25, lead into absorber 2 through sets of spray jets 4 and 5. Tn this line of circulation is a pump 32, and by this pump a circulation of menstruum may be completed which in a sense forms an eddy in the flowing stream of menstruum. That is tofsay, the stream of menstruum advancing through pipe 22 and header 25 into the absorber 2, before it advances from absorber 2 through pipe 31 into the vent, is by means of the pump 32 caused to flow in a closed circuit from absorber v2 through sump 29, pipe 33, header 36 and 37, back again into absorber 2. Tt will be understood that during all the time of operation `(at least, with the apparatus arranged as preferred) menstruum will be' streaming into absorber 2 and also streaming out through sump 29 and pipe 31, but the condition 1s such that the main stream Hows relatively slowly, while, by reason of the speed of the pump 32, the circulation spoken of as the eddy is coursing rapidly, and consequently substantially the same bodies of menstruum are being sprayed again and again into the absorber 2, and again and again come into absorption contact with the advancing stream of gasoline laden gas. It will further be observed that the spray nozzles 3, 4, and 5 provide for minute division of the menstruum as it enters' the absorber 2, and so for extended areas of contact in the first absorber between menstruum and gas.

The rates of flow in the various parts of the circuit of menstruum are determined by the several pumps, and particularly pumps 18, 20 and 32. The flowing material may be available for test purposes by the provision of a pet cock 24 at the delivery side of the second absorber, and a pet cock 40 at the delivery side ofthe first absorber. As we have said itis desirablev to have a decrease in specific gravity of the menstruum as 'it passes through absorber9, such as would be indicated by a rise of 1 in Baume scale or thereab'outs, While in the first absorber it is desirable to have a much greater absorption, such as would be indicated by a rise of 6 or 8 on the Baume scale, or therea-bouts (a rise unprecedented, and but for our improved apparatus impossible). According to 'tests of material drawn off as the operation progresses at taps 23, 24E, and 40, and,

by means of regulation of speed of the several pumps, the apparatus as a Whole may be brought to a condition in which such relative degrees of absorption-as rwe have specitied may be brought about. p

Referring to the circulation system through the first absorber, which consists of sump 29, pump 32, pipe 33, and its connections, more minute description is desirable. The pipe 33 leads to a header 34, and this header in turn, by means of branch pipes 54 and 35, leads to branch headers 36 and 37, from which the two sets of spray nozzles 4 and 5 open. The pipes 54 and 35 are preferably providedwith controlling valves 39, and the spray nozzles 5 are preferably constructed -to divide the menstruum into a ner spray than do the spray nozzles 4. Preferably also the spray .nozzles 4 divide the menstruum into a finer spray than do the nozzles 3. By proper regulation of valves` 439, the flow of menstruum through the ynozzles 4t and 5 may be controlled, to eiiect this desired dilerence in ineness of the spray issuing from the three sets of nozzles 3, 4, and 5, the preferred arrangement being such that the entering gas first meets the finest spray and progressively meets that less and less tine.

The pump 32 is of capacity such and run at a speed such that :it causes the menstruum to circulate at a speed to ali'ord, under the existing conditions of valve setting, the desired amount of absorption in absorber 2. Approximately speaking, the same bodies of menstruum by means of this eddy come again and again in Contact with the stream of gas, and, if it be desired to obtain say six4v contacts of menstruum, or if the menstruum as it meets the gas is to be (to the extent of tive-sixths of its volume) the same body which has already contacted with the gas, the pump 32- will be so operated that thenumber of gallons of menstruum pumped by it per minute will be six times the number ot gallons of menstruum entering the absorber through sprays 3.

Recurring to the matter of the actual iigures representing decrease in specific gravity of the circulating stream oi menstruum in the first absorber, we have found it to be true that, with natural gas which contains initially about five hundred gallons oi gasoline per million cubic feet of gas, it is advantageous to eti'ect in the first absorber a decrease in specific gravity such as is represented by a rise of as much as 8 on the Baume scale. This value may be departed from as circumstances dictate, according as the amount of gasoline carried in the gas varies.

In the ensuing claims we speak of a yfirst body of menstruum and a second body oi menstruum, and by the second body of menstruum we means that in the absorber 9. By the first body ot menstruum we mean that in the absorber 2, together with (in case it be used) that in the coke tower l2. y

It remains to be shown that the apparatus used admits of variation in the specific torni. Referring to Figure 2, there will be seen illustrated in it an alternative form for the second absorber, that is the absorber which in Figure l is marked 9. In this case this second absorber takes the form of a coke tower 56 of familiar construction, suihciently described already. The circulating menstruum entering throughthe pipe 19a is subdivided, and caused to percolate through the body of broken inert material 57. De-

scending through this it gathers at the bottom of the tower and passes on through the y pipe 21 to the `first absorber. j At the same time, the gas from the first absorber enters the coke tower 56 through pipe 6a and rises through -the body of inert broken material 57, where it gives up substantially all of its remaining burden of gasoline. From the coke tower it passes on through the pipe l0a "to the point of consumption. ln the upper part of the coke tower are arranged battle plates 59, to detain and return to the stream of menstruum small particles of menstruum which might otherwise be carried on by the gas. More particularly, the details of Figure 2 designated by numerals followed by the letters a correspond respectively to the parts which in Fi designated by the' same numera s.

Instead of using separate vessels tor the first and second bodies of menstruum, a single vessel may be used, such as, for eX- ample, that shown in Figure 3. The single structure wherein the two absorption steps.

relare already described are carried on is there with the description of Figure l, characterized by the term feddy, or through the pipe i 31b to vent tank and still.

A word will suiiice 'to explain the eddy here. A.' pump 32Ib causes the menstruum which Hows through pipe 30 to circulate through pipe 33h, and enter the coke tower again at a point about midway its height. As beforez a rapid circulation through this eddy line will effect the repeated lcontacts of substantially the same bodies of menstruum again and again with the flowing stream ofgas. Avent tank 66. maybe placed in this eddy circuit if desired, for'the obvious purpose of venting li hter combustible constitu-l ents which have een absorbed and carried out of the coke tower in the menstruum. The use ofv a vent tankfatthis point does not preclude the use of another vent tank such'as 42 in 'Figure 1. Oneor both may 'be used as found desirable. And a vent tank 66 may be added, if desired, to the assembly of parts shown in Fig. 1. As before, both pipe con'- nections 30b and 31b are at all times open, the circulation is continuous, and it is a matter ofcontrolling the valve ports and the speeding of the pumps which brings about-- the circulation and absorption which I have already defined. Between the through line 31b and the iniow through pipe 19h, the same apparatus for treating the menstruum .as that shown in Figure 1, with' the variations already suggested, are placed. The gas enters this tower 60 from the line 1a, Hows upwardly, and out through the lead 10a. .In the Ilower half the stream of gas meets relativlely large quantities of menstruum flowing rapidly in the upper part it meets relatively small quantities of menstruum flowin slowly. The ,sameA opportunities are a orded for testing the specific gravity of the menstruum at successive` points, in the presence of the pet cocks 23", 64, and 40".

vIt will be seen that the second body of menstruum may be either in the form of a pool, (Figure 1),or in subdivided state (Figure 3) when brought into contact with the gas. It will further be seen that the first and the second bodies of menstruum may be maintained in the same (Figure 3) yor in separate (Figure 1) vessels. It will further be seen that the circulating stream of menstruum may be arrested and dammed(Fig ure l) to affordv absorbing conditions, or it the outflow may How without any such backing up of the stream as'the use of the term dam imports (Figure 3), to afford absorbing conditions. It is clear from the consideration of the apparatus of Figure 1 that a plurality of absorbers may be used to effect the first absorption and, manifestly, without further illustration, the number and type of such a plurality of absorbers may be changed as desired. In all cases, however, there 1s a small loss in specific gravity of the menstruum passing through the second absorber, as comgered with the loss which it undergoes in the rst absorber, and means are available for controlling and varying the relative degree of absorption in the two absorbers.

We have found it impossible to absorb from the gas absolutely all of the gasoline which is borne b it, for the reason that the gasoline absorbe by the menstruum will always have a certain vapor tension, and when in the progress of absorption the point is reached where the vapor tension of the absorbed gasoline' equalsy the partial pressure of the asoline remaining in the gas, absorptionv wi l cease. Hence there always remains in the gas after it has Apassed through the last absorber some vestige of-the original.;- gasoline burden. We havev found, however, that 'this remaining vestige may Vbe made very small by the method performed in the apparatus now described.

s-a specific example of how completely gasollne may be absorbed from the gas by t e apparatus of our invention, we have in actual operation a plant in lwhich 96.6% of the asoline burden ofthe gas is recovered. uring a days run in which this percentage was recovered 19,000 cubic feet of' gas were passing per hour through the two bodies of menstruum. The menstruum consisted of liquid petroleum having a gravity before absorption of about 39 B. The pressure of the gas ranged from 56 to 61 pounds above atmospheric pressure, and the temperature under which absorption was performed ranged from 52 to 66 F. The first body of menstruum was circulated, in what I have termed the eddy system of circulation, through the spray absorbers four times .as fast as the menstruum from the second ab, sorber entered the first. The loss in specific gravity of the menstruum in the first absorber was that indicated by a rise of 6.7 on theBaum scale, While the loss in the second absorber was indicated by a rise of 1 on the same scale. The gas before being treated contained 767 gallons of gasoline per million cubic feet, and 7 41 gallons per million cubic feet were recovered. The apparatus used was ofthe. type and of the arrangement shown in Figure 1 of the accompanying drawings, including the coke tower indicated by numeral 12. 354L gallons of oil per hour were caused to iiow through the pool absorber, a rate second absorber `Will mean of course an in-v which, dierently stated, is about one gallon of oil to 54 cubic feet of gas.

From what has been said it is apparent that the rate of flow of menstruum is, in the practice of our apparatus, controlled in accordance with the loss of specific gravity in passing through the. second absorber. 'Ifsuch loss is greater than is permissible, according to the standards already set, then the conditions of absorption in the irstla-bsorber should be niodilied,in this case made more avorable'to absorption, either by speeding up the eddy circulation or by more inely subdividing the menstruum in the spray. If by such means, correction is not eected, and the loss in specific gravity reduced within permissible range, then fthe rate of tlovv of menstruum through the sec,-

ond absorber should be increased. Such lan increase of flow of menstruum through the conditions made more favorable to absorp.

tion.

In the practice of our invention the gas may be treated under anydesired pressure.

As compared With the amount of gasoline recovered from the gas 'When under treatment at` the customary pressures of ity' or more pounds per square inch above atmospher'ic pressure, We have found'that as much gasoline may be recovered under a pressure of twenty pounds or less above atmospheric pressure, provided only that the conditions of absorption in the first absorber` be suiiciently favorable, and rovided 'that the relative changes in speci' c gravity in the second absorber be controlled in the manner and to the e'ect described above. Y

It Will be observed that With the apparatus now described the stream of gas, advancing counter-current -to the stream of menstruum, meets the stream of menstruum as successive points; that superior conditions of absorption are maintained Where the gas initially encounters the menstruum, as compared with the conditions Where it ultimately encounters it. These superior conditions result rom the formation and maintenance of the eddy in the stream of menstruum so that the same bodies of menstruum come repeatedly into absorption-affording contact with the gas.

It will further be noted that by varying the speed of the pumps according to gravity readings We may cause to vary the absorption conditions of the first contact of gas with menstruum, relatively to those of thev ultimate contact.

We have in the foregoing specification described our invention in specific applicat1on .to an apparatus for recovering commercial gasoline rom natural gas. It will be understood, Without further elucidation,

than that of the recovered liquid, and indeed in case of the recovery of benzole from the gases Which ordinarily carry it in vapor lform, the absorbent liquid used will ordinarily be a liquid of less speciic gravity than the benzole recovered. Accordingly, in such case, as the operation of our apparatus progresses, the menstruum will not, as in the case of gasoline recovery, decrease. in speciic` gravity, but will in fact increase in speciiic gravity, and in such case it will be understood that the Aprocess is accomplished in so adjusting the apparatus, and so governing the operation relatively part to part, thaty the specific gravity of that body of menstruum through which the stream of gas first passes Will increase (not decrease) through a Wider range than Will the specific gravity of that portion or body of menstruum through which the gas iinally passes.

We claim as our invention:

1. In apparatus for the recovery of a substance normally liquid from a gas carrying it in vapor form, means for forming an eddy in a flowing stream of vapor-absorbing menstruum, together with means -for causing a stream of vapor-laden gas to flow first through the eddy and subsequently through the menstruum at a point farther upstream, substantially as described.

2. 'In apparatus for the recovery of a i substance normally liquid fromv a gas carrying it in vapor form, means for maintaining two bodies of vapor-absorbing menstruum, means for conducting a stream of vapor-laden gas through said bodies of menstruum successively, means for circulating the body of menstruum through which the gas rst passes to contactwith the gas a plurality of ltimes and means for varying the rate of such circulation independently of any circulation of the other body ot' menstruum, substantially as described.

3. In apparatus for the recovery of a substance normally liquid from a gas carrying it in vapor form, the combination of two absorbers connected by conduits for gas and for liquid, a gas supply and a liquid discharge conduit communicating with one of said absorbers and a liquid supply and a 5 to the t absorber first reached by the gas,

gas discharge communicatingI with the In testimony whereof We have hereunto `10 other, a valve i'n the liquid supply plpe set ou`r hands. leading to the absorber last named, a, by- JAMES B; 'GARNER pass for liquid leading from and back again SYLVESTER C. PRESTON.

'and'means for effecting circulation of liquid AVVtness.: insaid by-pass, substantially as' described.- FRANCIS TOMASSON4 

